Hi all, Those of you that know our car, know that its a street/strip car with 910hp TA tomahawk motor in it. Well we have just returned from a 500mile round trip without any issues. Most of it at 60mph (speed limit). It runs nice and smooth on the freeway and didnt get over 200 deg. I changed out the 4.11 gears for a set of 2.75 gears in the rear to help it cruise easier. Extremely happy with the hole deal. Managed 8gal to 60miles fuel usage (E85) was going to use the term 'economy' LOL Cheers
This strike anyone else as odd? Using E85 which should have way less heat than gasoline, yet he's still running upwards of 200 degrees Getting just over 7 mpg even with highway gears I would have expected the engine to run cold--right at the thermostat rating Poor fuel economy is a given with E85, but I'm not sure I'd expect economy THAT bad, at such a moderate speed. This thing is just screaming "not enough spark advance" to me. Curious: What thermostat is being used? How much vacuum advance (degrees + vacuum level for full advance) Ported or manifold vacuum? Maybe I have no idea what I'm talking about.
General comment... When only driving 60 with engines like this and a low numerical gear, I've seen much improved mileage in second gear. Awesome fun times diving them though! Can't say enough good things about this car.
I haven't had much experience driving race motors on the street. My ignition module has a curve that brings in total at 3800rpm. Locked distributor. Thermostat is a 160'f. The engine oil has always been an issue with high temps until I mounted a larger oil cooler in front of the radiator, which then loads up the radiator temp. Couldn't put it anywhere else so then I upgraded the Spal fan to the strongest 16" fan. Hope this may explain Cheers
OK, no vacuum advance, engine is running off of a "race" ignition curve. 60 mph and highway gears, (low cruise RPM) with an advance curve that doesn't stop bringing in advance until 3,800 rpm is not optimum. 1. I don't know how E-85 burns. My suspicion is that it burns slower than gasoline. Therefore more advance needed. More compression, too. 2. Any engine that runs at part-throttle can benefit from vacuum advance--or the electronic equivalent. Better throttle response, cleaner plugs, improved fuel economy. Likely lower engine temperature, too. 3. You're close to 40 degrees above the thermostat rating at cruise. You should be within about five degrees. There is SOMETHING wrong. My suspicion is nowhere near enough ignition advance at cruise, but I suppose we could also be talking water pump, radiator condition and size, airflow ducting in the engine compartment, etc. A single 16" electric fan does not seem like enough, but at 60 mph, you shouldn't need a fan. Wild-ass Guess: You get enough ignition advance, you'll need a 180 thermostat just to get the engine up-to-temperature, and your oil temp problems are gone. Someone here knows more about E85 than I do. What is your compression ratio? With E85, I hope it's 12:1 or maybe higher.
Seems to me what we really need to know is what is the ignition timing at your cruise RPM. Might take you 5 minutes or less with a timing light. BTW, what kind of ignition system are you running?
I'm not familiar with that ignition? What are your options for advance curves, and how are they adjusted? Does it have a vacuum advance option? Running the engine with retarded timing will heat it up.
Yes there are different curves. Without confirming it with my engine builder, I believe initial is 20' with 9' coming in by 3800rpm. Here are the different curves
